It’s Probably Not the Sirtuins
The life-extension effect induced through caloric restriction (CR) or intermittent fasting (IF) has been studied more extensively in animal models than amongst human subjects — people just live too darn long for quick study results. A couple years ago researchers suggested that sirtuins might be responsible for the longevity effect observed in CR and IF.
Then came a study that showed fruit flies lived longer on a calorie restricted regime when Sir2 was absent — the opposite of the expected effect. Sir2 is a sirtuin in fruit flies that corresponds to SirT1 in mammals. Now further research indicates that brain cells from rats react better to oxidative stress when SirT1 is not present, suggesting that elderly brains may be harmed by the presence of SirT1.
Sirutuins like Sir2 and SirT1 play a complex role in metabolism, and their activity can not be clearly categorized as either beneficial nor harmful to longevity. More likely, they have some effect on processes that directly affect lifespan, such as glucose metabolism, antioxidant activity and insulin sensitivity.
Biologists are looking for the ’smoking gun’ (or guns) responsible for aging. It’s probably not the sirtuins, though they do play some role in the process. It can seem disheartening to see a promising line of research lead to a seeming dead-end, but in science negative results can sometimes be as helpful as positive findings, in that it further narrows the field and helps better focus attention on relevant factors.
